Illumination devices comprising a transmissive arrangement with a luminescent material are known in the art. Transmissive ceramic layers or luminescent ceramics, and their method of preparation, are known in the art. It is for instance referred to US2005/0269582, US2006/0202105), to WO2006/097868, to WO2007/080555, to US2007/0126017 and to WO2006/114726.
US2005/0269582 for instance, discloses a semiconductor light emitting device combined with a ceramic layer which is disposed in a path of light emitted by the light emitting layer. The ceramic layer is composed of or includes a wavelength converting material such as a luminescent material.
Further, US2008029720 describes a lighting arrangement which comprises: an LED chip, configured to emit radiation having a first wavelength range; a luminescent material, configured to absorb at least a portion of said first wavelength range radiation and to emit radiation having a second wavelength range; and an optical component, through which at least said first wavelength range radiation passes. The LED is characterized in that the luminescent material is provided on a surface of the optical component.
WO2005083036 describes an LED lamp including an LED and one or more luminescent materials, wherein for each luminescent material, a figure of merit (FOM) defined as the product of (incident LED flux)×(excitation cross-section of the luminescent material)×(luminescent material decay time) is less than 0.3. Such a transmissive arrangement is assumed to provide a light emitting device with improved lumen output and colour stability over a range of drive currents.
Further, luminescent multilayers are known in the in the art. US2004217692 for instance describes a light-emitting device including a light source outputting an excitation light and a fluorescent multilayer having at least two fluorescent layers emitting different wavelengths in response to the excitation light. A fluorescent layer emitting a longer wavelength and/or having a lower light conversion efficiency than other fluorescent layers is adjacent to the light source. A fluorescent layer emitting a shorter wavelength and/or having a higher light conversion efficiency than other fluorescent layers, is farthest from the light source. Accordingly, it is possible to increase the overall light conversion efficiency of the light-emitting device and the amount of light output from the light-emitting device.
U.S. Pat. No. 7,213,940 describes a lighting device comprising first and second groups of solid state light emitters, which emit light having dominant wavelength in ranges of from 430 nm to 480 nm and from 600 nm to 630 nm, respectively, and a first group of lumiphors which emit light having dominant wavelength in the range of from 555 nm to 585 nm. If current is supplied to a power line, a combination of light exiting the lighting device which was emitted by the first group of emitters, and light exiting the lighting device which was emitted by the first group of lumiphors would, in an absence of any additional light, produce a sub-mixture of light having x, y colour coordinates within a specific area on a 1931 CIE Chromaticity Diagram.